Suppose a car travels 108 km at a speed of 35.0 m/s, and uses 1.80 gallons of gasoline. Only 30% of the gasoline goes into useful work by the force that keeps the car moving at constant speed despite friction. (The energy content of gasoline is 1.3 ✕ 108 J per gallon.)(a) What is the force exerted to keep the car moving at constant speed?  N(b) If the required force is directly proportional to speed, how many gallons will be used to drive 108 km at a speed of 28.0 m/s?  gallons

A mechanic pushes a 2.60 ✕ 103-kg car from rest to a speed of v, doing 4,950 J of work in the process. During this time, the car moves 22.0 m. Neglecting friction between car and road, find v and the horizontal force exerted on the car. (a) the speed v m/s (b) the horizontal force exerted on the car (Enter the magnitude.) N

A mechanic pushes a 2.40 ✕ 103-kg car from rest to a speed of v, doing 5,340 J of work in the process. During this time, the car moves 26.0 m. Neglecting friction between car and road, find v and the horizontal force exerted on the car. (a) the speed v m/s (b) the horizontal force exerted on the car (Enter the magnitude.) N

As usual, Hampus is out cycling. He is driving at 30.0 km/ h when he comes to a small hill that is 11 m high and 350 m long. Hampus and the bike weigh 95 kg together. a) What kinetic energy does Hampus have just before the hill? b) How much extra energy must Hampus produce to maintain a constant speed (30.0 km/ h) throughout the hill? c) How long does it take him to drive up the hill? d) What effect must he develop on the hill? Once at the top of the hill, the ground is flat. Hampus is tired and stops pedaling. After 12s the cycle stops. e) How big is the coefficient of friction? You can assume that is constant throughout the deceleration and that it includes both drag and rolling resistance.